4(Phenyl-piperazinyl-methyl) benzamide derivatives and their use for the treatment of pain or gastrointestinal disorders

ABSTRACT

Compounds of general formula: wherein R 1  and R 2  are as defined in the specification, as well as salts, enantiomers thereof and pharmaceutical compositions including the compounds are prepared. They are useful in therapy, in particular in the management of pain.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to novel compounds, to a process fortheir preparation, their use and pharmaceutical compositions comprisingthe novel compounds. The novel compounds are useful in therapy, and inparticular for the treatment of pain, anxiety and functionalgastrointestinal disorders.

2. Discussion of Relevant Art

The δ receptor has been identified as having a role in many bodilyfunctions such as circulatory and pain systems. Ligands for the δreceptor may therefore find potential use as analgesics, and/or asantihypertensive agents. Ligands for the δ receptor have also been shownto possess immunomodulatory activities.

The identification of at least three different populations of opioidreceptors (μ, δ and κ) is now well established and all three areapparent in both central and peripheral nervous systems of many speciesincluding man. Analgesia has been observed in various animal models whenone or more of these receptors has been activated.

With few exceptions, currently available selective opioid δ ligands arepeptidic in nature and are unsuitable for administration by systemicroutes. One example of a non-peptidic δ-agonist is SNC80 (Bilsky E. J.et al., Journal of Pharmacology and Experimental Therapeutics, 273(1),pp. 359-366 (1995)).

Many δ agonist compounds that have been identified in the prior art havemany disadvantages in that they suffer from poor pharmacokinetics andare not analgesic when administered by systemic routes. Also, it hasbeen documented that many of these δ agonist compounds show significantconvulsive effects when administered systemically.

U.S. Pat. No. 6,130,222 to Roberts et al. describes some δ-agonists.

However, there is still a need for improved δ-agonists.

DETAILED DESCRIPTION OF THE INVENTION DEFINITIONS

Unless specified otherwise within this specification, the nomenclatureused in this specification generally follows the examples and rulesstated in Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F,and H. Pergamon Press, Oxford, 1979, which is incorporated by referencesherein for its exemplary chemical structure names and rules on namingchemical structures.

The term “C_(m-n)” or “C_(m-n) group” used alone or as a prefix, refersto any group having m to n carbon atoms.

The term “hydrocarbon” used alone or as a suffix or prefix, refers toany structure comprising only carbon and hydrogen atoms up to 14 carbonatoms.

The term “hydrocarbon radical” or “hydrocarbyl” used alone or as asuffix or prefix, refers to any structure as a result of removing one ormore hydrogens from a hydrocarbon.

The term “alkyl” used alone or as a suffix or prefix, refers tomonovalent straight or branched chain hydrocarbon radicals comprising 1to about 12 carbon atoms. An “alkyl” may optionally contain one or moreunsaturated carbon-carbon bonds.

The term “alkylene” used alone or as suffix or prefix, refers todivalent straight or branched chain hydrocarbon radicals comprising 1 toabout 12 carbon atoms, which serves to links two structures together.

The term “alkenyl” used alone or as suffix or prefix, refers to amonovalent straight or branched chain hydrocarbon radical having atleast one carbon-carbon double bond and comprising at least 2 up toabout 12 carbon atoms.

The term “alkynyl” used alone or as suffix or prefix, refers to amonovalent straight or branched chain hydrocarbon radical having atleast one carbon-carbon triple bond and comprising at least 2 up toabout 12 carbon atoms.

The term “cycloalkyl,” used alone or as suffix or prefix, refers to amonovalent ring-containing hydrocarbon radical comprising at least 3 upto about 12 carbon atoms.

The term “cycloalkenyl” used alone or as suffix or prefix, refers to amonovalent ring-containing hydrocarbon radical having at least onecarbon-carbon double bond and comprising at least 3 up to about 12carbon atoms.

The term “cycloalkynyl” used alone or as suffix or prefix, refers to amonovalent ring-containing hydrocarbon radical having at least onecarbon-carbon triple bond and comprising about 7 up to about 12 carbonatoms.

The term “aryl” used alone or as suffix or prefix, refers to amonovalent hydrocarbon radical having one or more polyunsaturated carbonrings having aromatic character, (e.g., 4n+2 delocalized electrons) andcomprising 5 up to about 14 carbon atoms.

The term “arylene” used alone or as suffix or prefix, refers to adivalent hydrocarbon radical having one or more polyunsaturated carbonrings having aromatic character, (e.g., 4n+2 delocalized electrons) andcomprising 5 up to about 14 carbon atoms, which serves to link twostructures together.

The term “heterocycle” used alone or as a suffix or prefix, refers to aring-containing structure or molecule having one or more multivalentheteroatoms, independently selected from N, O, P and S, as a part of thering structure and including at least 3 and up to about 20 atoms in thering(s). Heterocycle may be saturated or unsaturated, containing one ormore double bonds, and heterocycle may contain more than one ring. Whena heterocycle contains more than one ring, the rings may be fused orunfused. Fused rings generally refer to at least two rings share twoatoms therebetween. Heterocycle may have aromatic character or may nothave aromatic character.

The term “heteroaromatic” used alone or as a suffix or prefix, refers toa ring-containing structure or molecule having one or more multivalentheteroatoms, independently selected from N, O, P and S, as a part of thering structure and including at least 3 and up to about 20 atoms in thering(s), wherein the ring-containing structure or molecule has anaromatic character (e.g., 4n+2 delocalized electrons).

The term “heterocyclic group,” “heterocyclic moiety,” “heterocyclic,” or“heterocyclo” used alone or as a suffix or prefix, refers to a radicalderived from a heterocycle by removing one or more hydrogens therefrom.

The term “heterocyclyl” used alone or as a suffix or prefix, refers amonovalent radical derived from a heterocycle by removing one hydrogentherefrom.

The term “heterocyclylene” used alone or as a suffix or prefix, refersto a divalent radical derived from a heterocycle by removing twohydrogens therefrom, which serves to links two structures together.

The term “heteroaryl” used alone or as a suffix or prefix, refers to aheterocyclyl having aromatic character.

The term “heterocylcoalkyl” used alone or as a suffix or prefix, refersto a heterocyclyl that does not have aromatic character.

The term “heteroarylene” used alone or as a suffix or prefix, refers toa heterocyclylene having aromatic character.

The term “heterocycloalkylene” used alone or as a suffix or prefix,refers to a heterocyclylene that does not have aromatic character.

The term “six-membered” used as prefix refers to a group having a ringthat contains six ring atoms.

The term “five-membered” used as prefix refers to a group having a ringthat contains five ring atoms.

A five-membered ring heteroaryl is a heteroaryl with a ring having fivering atoms wherein 1, 2 or 3 ring atoms are independently selected fromN, O and S.

Exemplary five-membered ring heteroaryls are thienyl, furyl, pyrrolyl,imidazolyl, thiazolyl, oxazolyl, pyrazolyl, isothiazolyl, isoxazolyl,1,2,3-triazolyl, tetrazolyl, 1,2,3-thiadiazolyl, 1,2,3-oxadiazolyl,1,2,4-triazolyl, 1,2,4-thiadiazolyl, 1,2,4oxadiazolyl, 1,3,4-triazolyl,1,3,4-thiadiazolyl, and 1,3,4-oxadiazolyl.

A six-membered ring heteroaryl is a heteroaryl with a ring having sixring atoms wherein 1, 2 or 3 ring atoms are independently selected fromN, O and S.

Exemplary six-membered ring heteroaryls are pyridyl, pyrazinyl,pyrimidinyl, triazinyl and pyridazinyl.

The term “substituted” used as a prefix refers to a structure, moleculeor group, wherein one or more hydrogens are replaced with one or moreC₁₋₆hydrocarbon groups, or one or more chemical groups containing one ormore heteroatoms selected from N, O, S, F, Cl, Br, I, and P. Exemplarychemical groups containing one or more heteroatoms include —NO₂, —OR,—Cl, —Br, —I, —F, —CF₃, —C(═O)R, —C(═O)OH, —NH₂, —SH, —NHR, —NR₂, —SR,—SO₃H, —SO₂R, —S(═O)R, —CN, —OH, —C(═O)OR, —C(═O)NR₂, —NRC(═O)R, oxo(═O), imino (═NR), thio (═S), and oximino (═N—OR), wherein each “R” is aC₁₋₆hydrocarbyl. For example, substituted phenyl may refer tonitrophenyl, methoxyphenyl, chlorophenyl, aminophenyl, etc., wherein thenitro, methoxy, chloro, and amino groups may replace any suitablehydrogen on the phenyl ring.

The term “substituted” used as a suffix of a first structure, moleculeor group, followed by one or more names of chemical groups refers to asecond structure, molecule or group, which is a result of replacing oneor more hydrogens of the first structure, molecule or group with the oneor more named chemical groups. For example, a “phenyl substituted bynitro” refers to nitrophenyl.

Heterocycle includes, for example, monocyclic heterocycles such as:aziridine, oxirane, thiirane, azetidine, oxetane, thietane, pyrrolidine,pyrroline, imidazolidine, pyrazolidine, pyrazoline, dioxolane, sulfolane2,3-dihydrofuran, 2,5-dihydrofuran tetrahydrofuran, thiophane,piperidine, 1,2,3,6-tetrahydro-pyridine, piperazine, morpholine,thiomorpholine, pyran, thiopyran, 2,3-dihydropyran, tetrahydropyran,1,4-dihydropyridine, 1,4-dioxane, 1,3-dioxane, dioxane, homopiperidine,2,3,4,7-tetrahydro-1H-azepine homopiperazine, 1,3-dioxepane,4,7-dihydro-1,3-dioxepin, and hexamethylene oxide.

In addition, heterocycle includes aromatic heterocycles, for example,pyridine, pyrazine, pyrimidine, pyridazine, thiophene, furan, furazan,pyrrole, imidazole, thiazole, oxazole, pyrazole, isothiazole, isoxazole,1,2,3-triazole, tetrazole, 1,2,3-thiadiazole, 1,2,3-oxadiazole,1,2,4-triazole, 1,2,4-thiadiazole, 1,2,4-oxadiazole, 1,3,4-triazole,1,3,4-thiadiazole, and 1,3,4-oxadiazole.

Additionally, heterocycle encompass polycyclic heterocycles, forexample, indole, indoline, isoindoline, quinoline, tetrahydroquinoline,isoquinoline, tetrahydroisoquinoline, 1,4-benzodioxan, coumarin,dihydrocoumarin, benzofuran, 2,3-dihydrobenzofuran, isobenzofuran,chromene, chroman, isochroman, xanthene, phenoxathiin, thianthrene,indolizine, isoindole, indazole, purine, phthalazine, naphthyridine,quinoxaline, quinazoline, cinnoline, pteridine, phenanthridine,perimidine, phenanthroline, phenazine, phenothiazine, phenoxazine,1,2-benzisoxazole, benzothiophene, benzoxazole, benzthiazole,benzimidazole, benztriazole, thioxanthine, carbazole, carboline,acridine, pyrolizidine, and quinolizidine.

In addition to the polycyclic heterocycles described above, heterocycleincludes polycyclic heterocycles wherein the ring fusion between two ormore rings includes more than one bond common to both rings and morethan two atoms common to both rings. Examples of such bridgedheterocycles include quinuclidine, diazabicyclo[2.2.1 ]heptane and7-oxabicyclo[2.2.1]heptane.

Heterocyclyl includes, for example, monocyclic heterocyclyls, such as:aziridinyl, oxiranyl, thiiranyl, azetidinyl, oxetanyl, thietanyl,pyrrolidinyl, pyrrolinyl, imidazolidinyl, pyrazolidinyl, pyrazolinyl,dioxolanyl, sulfolanyl, 2,3-dihydrofuranyl, 2,5-dihydrofuranyl,tetrahydrofuranyl, thiophanyl, piperidinyl,1,2,3,6-tetrahydro-pyridinyl, piperazinyl, morpholinyl, thiomorpholinyl,pyranyl, thiopyranyl, 2,3-dihydropyranyl, tetrahydropyranyl,1,4-dihydropyridinyl, 1,4-dioxanyl, 1,3-dioxanyl, dioxanyl,homopiperidinyl, 2,3,4,7-tetrahydro-1H-azepinyl, homopiperazinyl,1,3-dioxepanyl, 4,7-dihydro-1,3-dioxepinyl, and hexamethylene oxidyl.

In addition, heterocyclyl includes aromatic heterocyclyls or heteroaryl,for example, pyridinyl, pyrazinyl, pynmidinyl, pyridazinyl, thienyl,furyl, furazanyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, pyrazolyl,isothiazolyl, isoxazolyl, 1,2,3-triazolyl, tetrazolyl,1,2,3-thiadiazolyl, 1,2,3-oxadiazolyl, 1,2,4-triazolyl,1,2,4-thiadiazolyl, 1,2,4-oxadiazolyl, 1,3,4-triazolyl,1,3,4-thiadiazolyl, and 1,3,4 oxadiazolyl.

Additionally, heterocyclyl encompasses polycyclic heterocyclyls(including both aromatic or non-aromatic), for example, indolyl,indolinyl, isoindolinyl, quinolinyl, tetrahydroquinolinyl,isoquinolinyl, tetrahydroisoquinolinyl; 1,4-benzodioxanyl, coumarinyl,dihydrocoumarinyl, benzofuranyl, 2,3-dihydrobenzofuranyl,isobenzofuranyl, chromenyl, chromanyl, isochromanyl, xanthenyl,phenoxathiinyl, thianthrenyl, indolizinyl, isoindolyl, indazolyl,purinyl, phthalazinyl, naphthyridinyl, quinoxalinyl, quinazolinyl,cinnolinyl, pteridinyl, phenanthridinyl, perimidinyl, phenanthrolinyl,phenazinyl, phenothiazinyl, phenoxazinyl, 1,2-benzisoxazolyl,benzothiophenyl, benzoxazolyl, benzthiazolyl, benzimidazolyl,benztriazolyl, thioxanthinyl, carbazolyl, carbolinyl, acridinyl,pyrolizidinyl, and quinolizidinyl.

In addition to the polycyclic heterocyclyls described above,heterocyclyl includes polycyclic heterocyclyls wherein the ring fusionbetween two or more rings includes more than one bond common to bothrings and more than two atoms common to both rings. Examples of suchbridged heterocycles include quinuclidinyl, diazabicyclo[2.2.1]heptyl;and 7-oxabicyclo[2.2.1]heptyl.

The term “alkoxy” used alone or as a suffix or prefix, refers toradicals of the general formula —O—R, wherein R is selected from ahydrocarbon radical. Exemplary alkoxy includes methoxy, ethoxy, propoxy,isopropoxy, butoxy, t-butoxy, isobutoxy, cyclopropylmethoxy, allyloxy,and propargyloxy.

The term “amine” or “amino” used alone or as a suffix or prefix, refersto radicals of the general formula —NRR′, wherein R and R′ areindependently selected from hydrogen or a hydrocarbon radical.

Halogen includes fluorine, chlorine, bromine and iodine.

“Halogenated,” used as a prefix of a group, means one or more hydrogenson the group is replaced with one or more halogens.

“RT” or “rt” means room temperature.

In one aspect, the invention provides a compound of formula I,enantiomers thereof, diastereomers thereof and pharmaceuticallyacceptable salts thereof:

wherein

-   -   R¹ is an aryl, heteroaryl, substituted aryl or substituted        heteroaryl; and

R² is hydrogen, optionally substituted C₁₋₁₂alkyl, optionallysubstituted C₆₋₁₂aryl, or optionally substituted C₂₋₁₂heterocyclyl.

In one embodiment, the present invention provides a compound of formulaI,

wherein R¹ is selected from phenyl; pyridyl; thienyl; furyl; imidazolyl;triazolyl; pyrrolyl; thiazolyl; and N-oxido-pyridyl, optionallysubstituted with one or more groups selected from C₁₋₆alkyl, halogenatedC₁₋₆alkyl, —NO₂, —CF₃, C₁₋₆ alkoxy, chloro, fluoro, bromo, and iodo; and

R² is hydrogen or methyl.

In another embodiment, the present invention provides a compound offormula I,

wherein R¹ is selected from phenyl; pyridyl; thienyl; furyl; imidazolyl;pyrrolyl; and thiazolyl, optionally substituted with one or more groupsselected from C₁₋₆alkyl, halogenated C₁₋₆alkyl, —NO₂, —CF₃, C₁₋₆ alkoxy,chloro, fluoro, bromo, and iodo; and

R² is hydrogen or methyl.

In a further embodiment, the present invention provides a compound offormula I,

wherein R¹ is selected from phenyl; pyridyl; thienyl; furyl; imidazolyl;pyrrolyl; and thiazolyl; and

R² is hydrogen or methyl.

It will be understood that when compounds of the present inventioncontain one or more chiral centers, the compounds of the invention mayexist in, and be isolated as, enantiomeric or diastereomeric forms, oras a racemic mixture. The present invention includes any possibleenantiomers, diastereomers, racemates or mixtures thereof, of a compoundof Formula I. The optically active forms of the compound of theinvention may be prepared, for example, by chiral chromatographicseparation of a racemate, by synthesis from optically active startingmaterials or by asymmetric synthesis based on the procedures describedthereafter.

It will also be appreciated that certain compounds of the presentinvention may exist as geometrical isomers, for example E and Z isomersof alkenes. The present invention includes any geometrical isomer of acompound of Formula I. It will further be understood that the presentinvention encompasses tautomers of the compounds of the formula I.

It will also be understood that certain compounds of the presentinvention may exist in solvated, for example hydrated, as well asunsolvated forms. It will further be understood that the presentinvention encompasses all such solvated forms of the compounds of theformula I.

Within the scope of the invention are also salts of the compounds of theformula I. Generally, pharmaceutically acceptable salts of compounds ofthe present invention may be obtained using standard procedures wellknown in the art, for example by reacting a sufficiently basic compound,for example an alkyl amine with a suitable acid, for example, HCl oracetic acid, to afford a physiologically acceptable anion. It may alsobe possible to make a corresponding alkali metal (such as sodium,potassium, or lithium) or an alkaline earth metal (such as a calcium)salt by treating a compound of the present invention having a suitablyacidic proton, such as a carboxylic acid or a phenol with one equivalentof an alkali metal or alkaline earth metal hydroxide or alkoxide (suchas the ethoxide or methoxide), or a suitably basic organic amine (suchas choline or meglumine) in an aqueous medium, followed by conventionalpurification techniques.

In one embodiment, the compound of formula I above may be converted to apharmaceutically acceptable salt or solvate thereof, particularly, anacid addition salt such as a hydrochloride, hydrobromide, phosphate,acetate, fumarate, maleate, tartrate, citrate, methanesulphonate orp-toluenesulphonate.

The novel compounds of the present invention are useful in therapy,especially for the treatment of various pain conditions such as chronicpain, neuropathic pain, acute pain, cancer pain, pain caused byrheumatoid arthritis, migraine, visceral pain etc. This list shouldhowever not be interpreted as exhaustive.

Compounds of the invention are useful as immunomodulators, especiallyfor autoimmune diseases, such as arthritis, for skin grafts, organtransplants and similar surgical needs, for collagen diseases, variousallergies, for use as anti-tumour agents and anti viral agents.

Compounds of the invention are useful in disease states wheredegeneration or dysfunction of opioid receptors is present or implicatedin that paradigm. This may involve the use of isotopically labelledversions of the compounds of the invention in diagnostic techniques andimaging applications such as positron emission tomography (ET).

Compounds of the invention are useful for the treatment of diarrhoea,depression, anxiety and stress-related disorders such as post-traumaticstress disorders, panic disorder, generalized anxiety disorder, socialphobia, and obsessive compulsive disorder, urinary incontinence,premature ejaculation, various mental illnesses, cough, lung oedema,various gastro-intestinal disorders, e.g. constipation, functionalgastrointestinal disorders such as Irritable Bowel Syndrome andFunctional Dyspepsia, Parkinson's disease and other motor disorders,traumatic brain injury, stroke, cardioprotection following miocardialinfarction, spinal injury and drug addiction, including the treatment ofalcohol, nicotine, opioid and other drug abuse and for disorders of thesympathetic nervous system for example hypertension.

Compounds of the invention are useful as an analgesic agent for useduring general anaesthesia and monitored anaesthesia care. Combinationsof agents with different properties are often used to achieve a balanceof effects needed to maintain the anaesthetic state (e.g. amnesia,analgesia, muscle relaxation and sedation). Included in this combinationare inhaled anaesthetics, hypnotics, anxiolytics, neuromuscular blockersand opioids.

Also within the scope of the invention is the use of any of thecompounds according to the formula I above, for the manufacture of amedicament for the treatment of any of the conditions discussed above.

A further aspect of the invention is a method for the treatment of asubject suffering from any of the conditions discussed above, whereby aneffective amount of a compound according to the formula I above, isadministered to a patient in need of such treatment.

Thus, the invention provides a compound of formula I, orpharmaceutically acceptable salt or solvate thereof, as hereinbeforedefined for use in therapy.

In a further aspect, the present invention provides the use of acompound of formula I, or a pharmaceutically acceptable salt or solvatethereof, as hereinbefore defined in the manufacture of a medicament foruse in therapy.

In the context of the present specification, the term “therapy” alsoincludes “prophylaxis” unless there are specific indications to thecontrary. The term “therapeutic” and “therapeutically” should becontrued accordingly. The term “therapy” within the context of thepresent invention further encompasses to administer an effective amountof a compound of the present invention, to mitigate either apre-existing disease state, acute or chronic, or a recurring condition.This definition also encompasses prophylactic therapies for preventionof recurring conditions and continued therapy for chronic disorders.

The compounds of the present invention are useful in therapy, especiallyfor the therapy of various pain conditions including, but not limitedto: chronic pain, neuropathic pain, acute pain, back pain, cancer pain,and visceral pain.

In use for therapy in a warm-blooded animal such as a human, thecompound of the invention may be administered in the form of aconventional pharmaceutical composition by any route including orally,intramuscularly, subcutaneously, topically, intranasally,intraperitoneally, intrathoracially, intravenously, epidurally,intrathecally, intracerebroventricularly and by injection into thejoints.

In one embodiment of the invention, the route of administration may beorally, intravenously or intramuscularly.

The dosage will depend on the route of administration, the severity ofthe disease, age and weight of the patient and other factors normallyconsidered by the attending physician, when determining the individualregimen and dosage level at the most appropriate for a particularpatient.

For preparing pharmaceutical compositions from the compounds of thisinvention, inert, pharmaceutically acceptable carriers can be eithersolid and liquid. Solid form preparations include powders, tablets,dispersible granules, capsules, cachets, and suppositories.

A solid carrier can be one or more substances, which may also act asdiluents, flavoring agents, solubilizers, lubricants, suspending agents,binders, or table disintegrating agents; it can also be an encapsulatingmaterial.

In powders, the carrier is a finely divided solid, which is in a mixturewith the finely divided compound of the invention, or the activecomponent. In tablets, the active component is mixed with the carrierhaving the necessary binding properties in suitable proportions andcompacted in the shape and size desired.

For preparing suppository compositions, a low-melting wax such as amixture of fatty acid glycerides and cocoa butter is first melted andthe active ingredient is dispersed therein by, for example, stirring.The molten homogeneous mixture in then poured into convenient sizedmoulds and allowed to cool and solidify.

Suitable carriers are magnesium carbonate, magnesium stearate, talc,lactose, sugar, pectin, dextrin, starch, tragacanth, methyl cellulose,sodium carboxymethyl cellulose, a low-melting wax, cocoa butter, and thelike.

The term composition is also intended to include the formulation of theactive component with encapsulating material as a carrier providing acapsule in which the active component (with or without other carriers)is surrounded by a carrier which is thus in association with it.Similarly, cachets are included.

Tablets, powders, cachets, and capsules can be used as solid dosageforms suitable for oral administration.

Liquid form compositions include solutions, suspensions, and emulsions.For example, sterile water or water propylene glycol solutions of theactive compounds may be liquid preparations suitable for parenteraladministration. Liquid compositions can also be formulated in solutionin aqueous polyethylene glycol solution.

Aqueous solutions for oral administration can be prepared by dissolvingthe active component in water and adding suitable colorants, flavoringagents, stabilizers, and thickening agents as desired. Aqueoussuspensions for oral use can be made by dispersing the finely dividedactive component in water together with a viscous material such asnatural synthetic gums, resins, methyl cellulose, sodium carboxymethylcellulose, and other suspending agents known to the pharmaceuticalformulation art.

Depending on the mode of administration, the pharmaceutical compositionwill preferably include from 0.05% to 99% w (per cent by weight), morepreferably from 0.10 to 50% w, of the compound of the invention, allpercentages by weight being based on total composition.

A therapeutically effective amount for the practice of the presentinvention may be determined, by the use of known criteria including theage, weight and response of the individual patient, and interpretedwithin the context of the disease which is being treated or which isbeing prevented, by one of ordinary skills in the art.

Within the scope of the invention is the use of any compound of formulaI as defined above for the manufacture of a medicament.

Also within the scope of the invention is the use of any compound offormula I for the manufacture of a medicament for the therapy of pain.

Additionally provided is the use of any compound according to Formula Ifor the manufacture of a medicament for the therapy of various painconditions including, but not limited to: chronic pain, neuropathicpain, acute pain, back pain, cancer pain, and visceral pain.

A further aspect of the invention is a method for therapy of a subjectsuffering from any of the conditions discussed above, whereby aneffective amount of a compound according to the formula I above, isadministered to a patient in need of such therapy.

Additionally, there is provided a pharmaceutical composition comprisinga compound of Formula I, or a pharmaceutically acceptable salt thereof,in association with a pharmaceutically acceptable carrier.

Particularly, there is provided a pharmaceutical composition comprisinga compound of Formula I, or a pharmaceutically acceptable salt thereof,in association with a pharmaceutically acceptable carrier for therapy,more particularly for therapy of pain.

Further, there is provided a pharmaceutical composition comprising acompound of Formula I, or a pharmaceutically acceptable salt thereof, inassociation with a pharmaceutically acceptable carrier use in any of theconditions discussed above.

In a further aspect, the present invention provides a method ofpreparing a compound of formula I.

In one embodiment, the invention provides a process for preparing acompound of formula II,

comprising of the step of reacting a compound of formula In:

with R¹—CHO to form the compound of formula IIwherein

R¹ is an aryl, heteroaryl, substituted aryl or substituted heteroaryl.

In another embodiment, the invention provides a process for preparing acompound of formula IV,

comprising: reacting a compound of formula II,

with an akali metal hydroxide in non-aqueous solvent to form thecompound of formula IV:wherein

R¹ is an aryl, heteroaryl, substituted aryl or substituted heteroaryl.

Particularly, the compounds of the present invention can be preparedaccording to the synthetic routes as exemplified in Schemes 1 and 2.

In another embodiment, the compounds of the present invention can beprepared according to the synthetic routes as exemplified in Schemes 3and 4.

Biological Evaluation

The compounds of the invention are found to be active towards δreceptors in warm-blooded animal, e.g., human. Particularly thecompounds of the invention are found to be effective δ receptor ligands.In vitro assays, infra, demonstrate these surprising activities,especially with regard to agonists potency and efficacy as demonstratedin the rat brain functional assay and/or the human δ receptor functionalassay (low). This feature may be related to in vivo activity and may notbe linearly correlated with binding affinity. In these in vitro assays,a compound is tested for their activity toward δ receptors and IC₅₀ isobtained to determine the selective activity for a particular compoundtowards δ receptors. In the current context, IC₅₀ generally refers tothe concentration of the compound at which 50% displacement of astandard radioactive δ receptor ligand has been observed.

The activities of the compound towards κ and μ receptors are alsomeasured in a similar assay.

In vitro Model

Cell Culture

Human 293S cells expressing cloned human κ, δ and μ receptors andneomycin resistance are grown in suspension at 37° C. and 5% CO₂ inshaker flasks containing calcium-free DMEM10% FBS, 5% BCS, 0.1% PluronicF-68, and 600 μg/ml geneticin.

Rat brains are weighed and rinsed in ice-cold PBS (containing 2.5 mMEDTA, pH 7.4). The brains are homogenized with a polytron for 30 sec(rat) in ice-cold lysis buffer (50 mM Tris, pH 7.0, 2.5mM EDTA, withphenylmethylsulfonyl fluoride added just prior use to 0.5 MmM from a0.5M stock in DMSO:ethanol).

Membrane Preparation

Cells are pelleted and resuspended in lysis buffer (50 mM Tris, pH 7.0,2.5 mM EDTA, with PMSF added just prior to use to 0.1 mM from a 0.1 Mstock in ethanol), incubated on ice for 15 min, then homogenized with apolytron for 30 sec. The suspension is spun at 1000 g (max) for 10 minat 4° C. The supernatant is saved on ice and the pellets resuspended andspun as before. The supernatants from both spins are combined and spunat 46,000 g(max) for 30 min. The pellets are resuspended in cold Trisbuffer (50 mM Tris/Cl, pH 7.0) and spun again. The final pellets areresuspended in membrane buffer (50 mM Tris, 0.32 M sucrose, pH 7.0).Aliquots (1 ml) in polypropylene tubes are frozen in dry ice/ethanol andstored at −70° C. until use. The protein concentrations are determinedby a modified Lowry assay with sodium dodecyl sulfate.

Binding Assays

Membranes are thawed at 37° C., cooled on ice, passed 3 times through a25-gauge needle, and diluted into binding buffer (50 mM Tris, 3 mMMgCl₂, 1 mg/ml BSA (Sigma A-7888), pH 7.4, which is stored at 4° C.after filtration through a 0.22 m filter, and to which has been freshlyadded 5 μg/ml aprotinin, 10 μM bestatin, 10 μM diprotin A, no DTI).Aliquots of 100 μl are added to iced 12×75 mm polypropylene tubescontaining 100 μl of the appropriate radioligand and 100 μl of testcompound at various concentrations. Total (TB) and nonspecific (NS)binding are determined in the absence and presence of 10 μM naloxonerespectively. The tubes are vortexed and incubated at 25° C. for 60-75min, after which time the contents are rapidly vacuum-filtered andwashed with about 12 ml/tube iced wash buffer (50 mM Tris, pH 7.0, 3 mMMgCl₂) through GF/B filters (Whatman) presoaked for at least 2 h in 0.1%polyethyleneimine. The radioactivity (dpm) retained on the filters ismeasured with a beta counter after soaking the filters for at least 12 hin minivials containing 6-7 ml scintillation fluid. If the assay is setup in 96-place deep well plates, the filtration is over 96-placePEI-soaked unifilters, which are washed with 3×1 ml wash buffer, anddried in an oven at 55° C. for 2 h. The filter plates are counted in aTopCount (Packard) after adding 50 μl MS-20 scintillation fluid/well.

Functional Assays

The agonist activity of the compounds is measured by determining thedegree to which the compounds receptor complex activates the binding ofGTP to G-proteins to which the receptors are coupled. In the GTP bindingassay, GTP[γ]³⁵S is combined with test compounds and membranes fromHEK-293S cells expressing the cloned human opioid receptors or fromhomogenised rat and mouse brain. Agonists stimulate GTP[γ]³⁵S binding inthese membranes. The EC₅₀ and E_(max) values of compounds are determinedfrom dose-response curves. Right shifts of the dose response curve bythe delta antagonist naltrindole are performed to verify that agonistactivity is mediated through delta receptors. For human δ receptorfunctional assays, EC₅₀ (low) is measured when the human δ receptorsused in the assay were expressed at lower levels in comparison withthose used in determining EC₅₀ (high). The E_(max) values weredetermined in relation to the standard δ agonist SNC80, i.e., higherthan 100% is a compound that have better efficacy than SNC80.

Procedure for Rat Brain GTP

Rat brain membranes are thawed at 37° C., passed 3 times through a25-gauge blunt-end needle and diluted in the GTPYS binding (50 mM Hepes,20 mM NaOH, 100 mM NaCl, 1 mM EDTA, 5 mM MgCl₂, pH 7.4, Add fresh: 1 mMDTT, 0.1% BSA). 120 μM GDP final is added membranes dilutions. The EC₅₀and E_(max) of compounds are evaluated from 10-point dose-responsecurves done in 300 μl with the appropriate amount of membrane protein(20 μg/well) and 100000-130000 dpm of GTPγ³⁵S per well (0.11-0.14 nM).The basal and maximal stimulated binding are determined in absence andpresence of 3 μM SNC-80

Data Analysis

The specific binding (SB) was calculated as TB-NS, and the SB in thepresence of various test compounds was expressed as percentage ofcontrol SB. Values of IC₅₀ and Hill coefficient (n_(H)) for ligands indisplacing specifically bound radioligand were calculated from logitplots or curve fitting programs such as Ligand, GraphPad Prism,SigmaPlot, or ReceptorFit. Values of K_(i) were calculated from theCheng-Prussoff equation. Mean±S.E.M. values of IC₅₀, K_(i) and n_(H)were reported for ligands tested in at least three displacement curves.Biological activity of the compounds of the present invention isindicated in Tables 1 and 2. TABLE 1 Human δ RAT BRAIN (nM) (nM) Ex.EC₅₀ % EMax Human κ Human μ % # IC₅₀ (high) (high) IC₅₀ IC₅₀ EC₅₀ EMax1a 0.26 0.29 101 112 7.7 0.2 170

TABLE 2 Human δ (nM) Ex. EC₅₀ % EMax Human κ Human μ # IC₅₀ (low) (low)IC₅₀ IC₅₀ 1b, 2a 0.14-3.73 0.5-83 91-104 396->10000 45-1718 2b, 3a and3bReceptor Saturation Experiments

Radioligand Kδ values are determined by performing the binding assays oncell membranes with the appropriate radioligands at concentrationsranging from 0.2 to 5 times the estimated Kδ (up to 10 times if amountsof radioligand required are feasible). The specific radioligand bindingis expressed as pmole/mg membrane protein. Values of Kδ and B_(max) fromindividual experiments are obtained from nonlinear fits of specificallybound (B) vs. nM free (F) radioligand from individual according to aone-site-model.

Determination of Mechano-Allodynia Using Von Frey Testing

Testing is performed between 08:00 and 16:00 h using the methoddescribed by Chaplan et al. (1994). Rats are placed in Plexiglas cageson top of a wire mesh bottom which allows access to the paw, and areleft to habituate for 10-15 min. The area tested is the mid-plantar lefthind paw, avoiding the less sensitive foot pads. The paw is touched witha series of 8 Von Frey hairs with logarithmically incremental stiffness(0.41, 0.69, 1.20, 2.04, 3.63, 5.50, 8.51, and 15.14 grams; Stoelting,Ill., USA). The von Frey hair is applied from underneath the mesh floorperpendicular to the plantar surface with sufficient force to cause aslight buckling against the paw, and held for approximately 6-8 seconds.A positive response is noted if the paw is sharply withdrawn. Flinchingimmediately upon removal of the hair is also considered a positiveresponse. Ambulation is considered an ambiguous response, and in suchcases the stimulus is repeated.

Testing Protocol

The animals are tested on postoperative day 1 for the FCA-treated group.The 50% withdrawal threshold is determined using the up-down method ofDixon (1980). Testing is started with the 2.04 g hair, in the middle ofthe series. Stimuli are always presented in a consecutive way, whetherascending or descending. In the absence of a paw withdrawal response tothe initially selected hair, a stronger stimulus is presented; in theevent of paw withdrawal, the next weaker stimulus is chosen. Optimalthreshold calculation by this method requires 6 responses in theimmediate vicinity of the 50% threshold, and counting of these 6responses begins when the first change in response occurs, e.g. thethreshold is first crossed. In cases where thresholds fall outside therange of stimuli, values of 15.14 (normal sensitivity) or 0.41(maximally allodynic) are respectively assigned. The resulting patternof positive and negative responses is tabulated using the convention,X=no withdrawal; O=withdrawal, and the 50% withdrawal threshold isinterpolated using the formula:50% g threshold=10^((Xf+kδ))/10,000where Xf=value of the last von Frey hair used (log units); k=tabularvalue (from Chaplan et al. (1994)) for the pattern of positive/negativeresponses; and 8=mean difference between stimuli (log units). Hereδ=0.224.

Von Frey thresholds are converted to percent of maximum possible effect(% MPE), according to Chaplan et al. 1994. The following equation isused to compute % MPE: ${\%\quad{MPE}} = {\frac{\begin{matrix}{{{Drug}\quad{treated}\quad{threshold}\quad(g)} -} \\{{allodynia}\quad{threshold}\quad(g)}\end{matrix}}{{{Control}\quad{threshold}\quad(g)} - {{allodynia}\quad{threshold}\quad(g)}} \times 100}$Administration of Test Substance

Rats are injected (subcutaneously, intraperitoneally, intravenously ororally) with a test substance prior to von Frey testing, the timebetween administration of test compound and the von Frey test variesdepending upon the nature of the test compound.

Writhing Test

Acetic acid will bring abdominal contractions when administeredintraperitoneally in mice. These will then extend their body in atypical pattern. When analgesic drugs are administered, this describedmovement is less frequently observed and the drug selected as apotential good candidate.

A complete and typical Writhing reflex is considered only when thefollowing elements are present: the animal is not in movement; the lowerback is slightly depressed; the plantar aspect of both paws isobservable. In this assay, compounds of the present inventiondemonstrate significant inhibition of writhing responses after oraldosing of 1-100 μmol/kg.

(i) Solutions Preparation

Acetic acid (AcOH): 120 μL of Acetic Acid is added to 19.88 ml ofdistilled water in order to obtain a final volume of 20 ml with a finalconcentration of 0.6% AcOH. The solution is then mixed (vortex) andready for injection.

Compound (drug): Each compound is prepared and dissolved in the mostsuitable vehicle according to standard procedures.

(ii) Solutions Administration

The compound (drug) is administered orally, intraperitoneally (i.p.),subcutaneously (s.c.) or intravenously (i.v.)) at 10 ml/kg (consideringthe average mice body weight) 20, 30 or 40 minutes (according to theclass of compound and its characteristics) prior to testing. When thecompound is delivered centrally: Intraventricularly (i.c.v.) orintrathecally (i.t.) a volume of 5 μL is administered.

The AcOH is administered intraperitoneally (i.p.) in two sites at 10ml/kg (considering the average mice body weight) immediately prior totesting.

(iii) Testing

The animal (mouse) is observed for a period of 20 minutes and the numberof occasions (Writhing reflex) noted and compiled at the end of theexperiment. Mice are kept in individual “shoe box” cages with contactbedding. A total of 4 mice are usually observed at the same time: onecontrol and three doses of drug.

For the anxiety and anxiety-like indications, efficacy has beenestablished in the geller-seifter conflict test in the rat.

For the functional gastrointestina disorder indication, efficacy can beestablished in the assay described by Coutinho S V et al, in AmericanJournal of Physiology—Gastrointestinal & Liver Physiology.282(2):G307-16, February 2002, in the rat.

Additional in vivo Testing Protocols

Subjects and Housing

Naïve male Sprague Dawley rats (175-200 g) are housed in groups of 5 ina temperature controlled room (22° C., 40-70% humidity, 12-hlight/dark). Experiments are performed during the light phase of thecycle. Animals have food and water ad libitum and are sacrificedimmediately after data acquisition.

Sample

Compound (Drug) testing includes groups of rats that do not receive anytreatment and others that are treated with E. colilipopolysaccharide(LPS). For the LPS-treated experiment, four groups areinjected with LPS, one of the four groups is then vehicle-treated whilstthe other three groups are injected with the drug and its vehicle. Asecond set of experiments are conducted involving five groups of rats;all of which receive no LPS treatment. The naive group receives nocompound (drug) or vehicle; the other four groups are treated withvehicle with or without drug. These are performed to determineanxiolytic or sedative effects of drugs which can contribute to areduction in USV.

Administration of LPS

Rats are allowed to habituate in the experimental laboratory for 15-20min prior to treatment. Inflammation is induced by administration of LPS(endotoxin of gram-negative E. coli bacteria serotype 0111:B4, Sigma).LPS (2.4 μg) is injected intracerebro-ventricularly (i.c.v.), in avolume of 10 μl, using standard stereotaxic surgical techniques underisoflurane anaesthesia. The skin between the ears is pushed rostrallyand a longitudinal incision of about 1 cm is made to expose the skullsurface. The puncture site is determined by the coordinates: 0.8 mmposterior to the bregma, 1.5 mm lateral (left) to the lambda (sagittalsuture), and 5 mm below the surface of the skull (vertical) in thelateral ventricle. LPS is injected via a sterile stainless steel needle(26-G 3/8) of 5 mm long attached to a 100 μl Hamilton syringe bypolyethylene tubing (PE20; 10-15 cm). A 4 mm stopper made from a cutneedle (20-G) is placed over and secured to the 26-G needle by siliconeglue to create the desired 5 mm depth.

Following the injection of LPS, the needle remains in place for anadditional 10 s to allow diffusion of the compound, then is removed. Theincision is closed, and the rat is returned to its original cage andallowed to rest for a minimum of 3.5 h-prior to testing.

Experimental Setup for Air-Puff Stimulation

The rats remains in the experimental laboratory following LPS injectionand compound (drug) administration. At the time of testing all rats areremoved and placed outside the laboratory. One rat at a time is broughtinto the testing laboratory and placed in a clear box (9×9×18 cm) whichis then placed in a sound-attenuating ventilated cubicle measuring62(w)×35(d)×46(h) cm (BRS/LVE, Div. Tech-Serv Inc). The delivery ofair-puffs, through an air output nozzle of 0.32 cm, is controlled by asystem (AirStim, San Diego Intruments) capable of delivering puffs ofair of fixed duration (0.2 s) and fixed intensity with a frequency of 1puff per 10 s. A maximun of 10 puffs are administered, or untilvocalisation starts, which ever comes first. The first air puff marksthe start of recording.

Experimental Setup for and Ultrasound Recording

The vocalisations are recorded for 10 minutes using microphones(G.R.A.S. sound and vibrations, Vedbaek, Denmark) placed inside eachcubicle and controlled by LMS (LMS CADA-X 3.5B, Data AcquisitionMonitor, Troy, Mich.) software. The frequencies between 0 and 32000 Hzare recorded, saved and analysed by the same software (LMS CADA-X 3.5B,Time Data Processing Monitor and UPA (User Programming and Analysis)).

Compounds (Drugs)

All compounds (drugs) are pH-adjusted between 6.5 and 7.5 andadministered at a volume of 4 ml/kg. Following compound (drug)administration, animals are returned to their original cages until timeof testing.

Analysis

The recording is run through a series of statistical and Fourieranalyses to filter (between 20-24 kHz) and to calculate the parametersof interest. The data are expressed as the mean ±SEM. Statisticalsignificance is assessed using T-test for comparison between naive andLPS-treated rats, and one way ANOVA followed by Dunnett's multiplecomparison test (post-hoc) for drug effectiveness. A difference betweengroups is considered significant with a minimum p value of ≦0.05.Experiments are repeated a minimum of two times.

EXAMPLES

The invention will further be described in more detail by the followingExamples which describe methods whereby compounds of the presentinvention may be prepared, purified, analyzed and biologically tested,and which are not to be construed as limiting the invention.

INTERMEDIATE 1: N,N-Diethyl-4-formylbenzamide

To a suspension of 4-carboxybenzaldehyde (30 g, 0.2 mole) in 100 ml oftoluene was added SOCl₂ (97 ml, 1.3 moles) at 60° C. The reaction washeated until gas evolution ceased followed by evaporation to drynesswith toluene (3×50 mL) This yielded a residue, which was dissolved inCH₂Cl₂ (200 mL). To this solution, cooled in an ice bath while stirring,was added diethylamine (50 mL). Stirring was continued for one hour andthen the mixture heated at reflux for a further hour. After cooling, themixture was washed successively with H₂O, 2 N HCl, H₂O then 2 N NaOH andfinally with H₂O. The solution was dried over MgSO₄, filtered andconcentrated to dryness yielding 41 g of oil. Distillation at 140-150°C./1.5 torr gave 36.9 g, 90 % of INTERMEDIATE 1.

INTERMEDIATE 2: 1-piperazinecarboxylic acid,4-[(3-cyanophenyl)[4-[(diethylamino)carbonyl]phenyl]methyl]-,1,1-dimethylethylester

To a dry flask containing N,N-diethyl-4-formyl-benzamide(INTERMEDIATE 1) (1.60 g, 1 eq), benzotriazole (929 mg, 1 eq) and1-piperazinecarboxylic acid, 1,1-dimethylethyl ester (1.45 g, 1 eq) wasadded dry toluene (50 mL) and the reaction was heated to reflux withwater removal. After 3.5 hours the reaction was cooled and concentratedto approximately 5 mL. The solution was diluted with tetrahydrofaran (5mL) and added slowly to a flask containing 3-cyanophenylzinc iodide(0.37 M solution in tetrahydrofuran, 42 mL, 2 eq). The reaction washeated to 50° C. for 20 hours then was cooled and quenched withsaturated aqueous ammonium chloride (50 mL). After 10 minutes themixture was extracted with dichloromethane (2×100 mL) and the combinedorganic extracts were then dried (MgSO₄), filtered and concentrated. Theresidue was purified by flash chromatography, eluting 3% methanol indichloromethane to yield INTERMEDIATE 2 as a yellow oil (2.120 g).

INTERMEDIATE 3:4-[(3-cyanophenyl)-1-piperazinylmethyl]-N,N-diethyl-benzamide

To a solution of INTERMEDIATE 2 (2.120 g) in dichloromethane (40 mL) wasadded trifluoroacetic acid (6.5 mL, 15 eq). After three hours at roomtemperature the reaction was quenched with aqueous sodium hydroxidesolution (1 N, 40 mL) and the organic layer was separated. The aqueouslayer was washed with dichloromethane (2×50 mL) and the combined organicextracts were dried (MgSO₄), filtered and concentrated. The residue waspurified by flash chromatography, eluting 10% to 20% methanol indichloromethane to yield INTERMEDIATE 3 as a colorless foam (1.113 g,39% over 3 steps).

INTERMEDIATE 4a:3-[(4-[(diethylamino)carbonyl]phenyl)(4-benzyl-piperazin-1-yl)methyl]benzonitrile

To a solution of INTERMEDIATE 3 (606 mg) in 1,2-dichloroethane (15 mL)was added benzaldehyde (220 μL, 1.3 eq) and sodium triacetoxyborohydride(480 mg, 1.4 eq). After 3 days the reaction was diluted withdichloromethane (50 mL) and washed with saturated aqueous sodiumbicarbonate. The aqueous layer was washed with dichloromethane (2×25 mL)and the combined organic extracts were dried (MgSO₄), filtered andconcentrated. The residue was purified by flash chromatography, eluting5% methanol in dichloromethane to yield INTERMEDIATE 4a as a colorlessfoam (428mg, 57%).

INTERMEDIATE 4b:3-{(4-[(diethylamino)carbonyl]phenyl)[4-(2-furylmethyl)-piperazin-1-yl]methyl}benzonitrile

To a solution of INTERMEDIATE 3 (567 mg) in 1,2-dichloroethane (15 mL)was added 2-furaldehyde (160 μL, 1.3 eq) and sodiumtriacetoxyborohydride (450 mg, 1.4 eq). After 3 days the reaction wasdiluted with dichloromethane (50 mL) and washed with saturated aqueoussodium bicarbonate. The aqueous layer was washed with dichloromethane(2×25 mL) and the combined organic extracts were dried (NgSO₄), filteredand concentrated. The residue was purified by flash chromatography,eluting 5% methanol in dichloromethane to yield INTERMEDIATE 4b as acolorless foam (367 mg, 53%).

INTERMEDIATE 5: 4-Iodo-N,N-diethylbenzamide

To a mixture of 4-iodo-benzoyl chloride (75 g) in 500 mL CH₂Cl₂ wasadded a mixture of Et₃N (50 mL) and Et₂NH (100 mL) at 0° C. After theaddition, the resulting reaction mixture was warmed up to roomtemperature in 1 hr and was then washed with saturated ammoniumchloride. The organic extract was dried (Na₂SO₄), filtered andconcentrated. Residue was recrystallized from hot hexanes to give 80 gof INTERMEDIATE 5.

INTERMEDIATE 6:3-[[4-[(diethylamino)carbonyl]phenyl]hydroxymethyl]-benzoic acid, methylester

INTERMEDIATE 5 (2.8 g, 9.0 mmol) was dissolved in TBF (100 mL) andcooled to −78° C. under nitrogen atmosphere. Then n-BuLi (8.4 mL, 1.07 Msolution in hexane, 9.0 mmol) was added dropwise during 10 min at −65 to−78° C. The solution was canulated into 3-carbomethoxybenzaldehyde (1.49g, 9.1 mmol) in toluene/THF (approx. 1:1, 50 mL) at −78° C. NH₄Cl (aq.)was added after 30 min. After concentration in vacuo, extraction withEtOAc/water, drying (MgSO₄) and evaporation of the organic phase, theresidue was purified by chromatography on silica (0-75% EtOAc/heptane)to give INTERMEDIATE 6 (1.5 g, 49%).

INTERMEDIATE 7: 1-piperazinecarboxylic acid,4-[[4-[(diethylamino)carbonyl]phenyl][3-(methoxycarbonyl)phenyl]methyl]-,1,1-dimethylethylester

To a solution of INTERMEDIATE 6 (1.5 g, 4.4 mmol) in dichloromethane (25mL) was added thionyl bromide (0.36 mL, 4.6 mmol). After one hour atroom temperature the reaction was washed with saturated aqueous sodiumbicarbonate (100 mL) and the organic layer was separated. The aqueouslayer was washed with dichloromethane (3×100 mL) and the combinedorganic extracts were dried (Na₂SO₄), filtered and concentrated.

The benzyl bromide was dissolved in acetonitrile (35 mL) and N-Bocpiperazine (0.9 g, 4.8 mmol) and triethylamine (0.67 mL, 4.8 mmol) wereadded. After heating the reaction for one hour at 65° C. the reactionwas cooled, washed with saturated amonium chloride/ethyl acetate and theorganic layer was separated. The aqueous layer was extracted with ethylacetate (3×100 mL) and the combined organic extracts were dried(Na₂SO₄), filtered and concentrated. The residue was purified by flashchromatography to give INTERMEDIATE 7 (2.04 g, 91%).

INTERMEDIATE 8:3-[[4-[(diethylamino)carbonyl]phenyl][4(phenylmethyl)-1-piperazinyl]methyl]-benzoicacid, methyl ester

To a solution of INTERMEDIATE 7 (2.0 g, 3.9 mmol) in dichloromethane (30mL) was added trifluoroacetic acid (15 mL). After 10 minutes thereaction was concentrated and the residue dissolved in dichloromethaneand washed with saturated aqueous sodium bicarbonate. The organicextract was dried (MgSO₄), filtered and concentrated.

The residue was dissolved in acetonitrile (25 mL) and benzyl bromide(475 μL, 4.0 mmol) and triethylamine (550 μL, 4.0 mmol) were added.After one hour at room temperature the reaction was concentrated,residue dissolved in dichloromethane and washed with water. The organiclayer was dried (MgSO₄), filtered and concentrated to give INTERMEDIATE8 (1.66 g, 85%).

INTERMEDIATE 9:3-[[4-[(diethylamino)carbonyl]phenyl][4-(phenylmethyl)-1-piperazinyl]methyl]-benzoicacid

To a solution of INTERMEDIATE 8 (1.66 g, 3.3 mmol) in methanol (15 mL)and water (5 mL) was added lithium hydroxide (0.69 g, 16.5 mmol). After5 hours at room temperature the methanol was removed and INTERMEDIATE 9was precipitated from the aqueous solution by the addition of 2Mhydrochloric acid. COMPOUND 1, 1a AND 1b:3-[(4-[(diethylamino)carbonyl]phenyl)(4-benzyl-piperazin-1-yl)methyl]benzamide

To a solution of INTERMEDIATE 4a (428 mg) in tert-butanol (10 mL) wasadded crushed potassium hydroxide (129 mg, 2.5 eq) and the reaction washeated to reflux. After 90 minutes the reaction was cooled and dilutedwith dichloromethane (40 mL). The reaction was washed with water (30 mL)and the organic layer separated. The aqueous layer was neutralized with2 N hydrochloric acid and washed with dichloromethane (2×25 mL). Thecombined organic extracts were dried (MgSO₄), filtered and concentrated.The residue was purified by flash chromatography, eluting 3% methanol indichloromethane to yield COMPOUND 1 as a colorless foam (374.5 mg, 84%).¹H NMR (CD₃OD) δ 1.06 (t, J=6.9 Hz, 3H), 1.20 (t, J=6.8 Hz, 3H),3.15-3.40 (m, 6H), 3.545-3.54 (m, 2H), 3.57-3.67 (m, 4H), 4.44 (s, 2H),5.39 (br s, 1H), 7.40 (d, J=8.4 Hz, 2H), 7.43-7.59 m, 6H), 7.82 (d,J=7.8 Hz, 3H), 7.93 (d, J=7.0 Hz, 1H), 8.22 (s, 1H).

COMPOUND 1 was separated by chiral HPLC to yield COMPOUNDS 1a and 1b,using a chiral AD column with 30% isopropanol 70% hexanes as an eluant,retention time being 11.3 minutes and 16.5 minutes for COMPOUNDS 1a and1b, respectively.

For COMPOUND 1a, Purity (HPLC): >99%; Optical purity (ChiralHPLC): >99%; Found: C, 58.93; H, 6.65; N, 8.82. C₃₀H₃₆N₄O₂×3.2HCl×0.6H₂Ohas C, 58.87; H, 6.65; N, 9.15%.

For COMPOUND 1b, Purity (HPLC): >99%; Optical purity (ChiralHPLC): >99%; Found: C, 58.88; H, 6.68; N, 8.94. C₃₀H₃₆N4O₂×3.1HCl×0.8H₂Ohas C, 58.87; H, 6.70; N, 9.15%

COMPOUNDS 2,2a and 2b:3-{(4-[(diethylamino)carbonyl]phenyl)[4-(2-furylmethyl)-piperazin-1-yl]methyl}benzamide

To a solution of INTERMEDIATE 4b (365 mg) in tert-butanol (10 mL) wasadded crushed potassium hydroxide (112 mg, 2.5 eq) and the reaction washeated to reflux. After 90 minutes the reaction was cooled and dilutedwith dichloromethane (40 mL). The reaction was washed with water (30 mL)and the organic layer separated. The aqueous layer was neutralized with2 N hydrochloric acid and washed with dichloromethane (2×25 mL). Thecombined organic extracts were dried (MgSO₄), filtered and concentrated.The residue was purified by flash chromatography to yield the racemicCOMPOUND 2 as a colorless foam. ¹H NMR (Free Amine) (400 MHz, CDCl₃): δ1.09 (br s, 3H), 1.20 br s, 3H), 2.47 (m, 8H), 3.23 (br s, 2H), 3.52 (brs, 2H), 3.55 (s, 2H), 4.31 (s, 1H), 5.63 (br s, 1H), 6.10 (br s, 1H),6.19 (d, J=2.9 Hz, 1 H), 6.30 (m, 1H), 7.27 (d, J=8.2 Hz, 2 H), 7.35 (m,2H), 7.41 (d, J=8.2 Hz, 2 H) 7.59 (m, 2H), 7.84 (s, 1H).

COMPOUND 2 was separated by chiral HPLC to yield COMPOUNDS 2a and 2b,using a chiral AD column with 30% isopropanol 70% hexanes as an eluant,retention time being 9.9 minutes and 12.9 minutes for COMPOUNDS 2a and2b, respectively.

For COMPOUND 2a, Purity (HPLC): >99%; Optical purity (ChiralHPLC): >99%. Found: C, 56.79; H, 6.65; N, 9.60. C₂₈H₃₄N₄O₃×2.6 HCl×1.3H₂O has C, 56.73; H, 6.67; N, 9.45%.

For COMPOUND 2b, Purity (HPLC): >99%; Optical purity (ChiralHPLC): >99%. Found: C, 57.86; H, 6.54; N, 9.56. C₂₈H₃₄N₄O₃×0.7HCl×3.1H₂O has C, 57.86; H, 6.76; N, 9.18%.

Alternative Synthesis of Compound 1

To a solution of INTERMEDIATE 9 (100 mg, 0.21 mmol) in dichloromethane(3 mL) at −20° C. was added isobutyl chloroformate (41 μL, 0.31 mmol)and triethylamine (43 μL, 0.31 mmol). After 10 minutes a solution ofammonia in dichloromethane (1.5M, 4.5 mL, 3 mmol) was added. Reacton waswarmed to room temperature and washed with brine. The organic layer wasdried (MgSO₄), filtered and concentrated to give COMPOUND 1.

COMPOUND 3, 3a AND 3b:3-[[4-[(diethylamino)carbonyl]phenyl][4-(phenylmethyl)-1-piperazinyl]methyl]-N-methyl-benzamide

To a solution INTERMEDIATE 9 (0.120 mg, 0.25 mmol)) in 2 ml of DMF wasadded HATU (0.132 mg, 0.35 mmol) and diisopropylethylamine (173 μL, 0.99mmol). The reaction was stirred for 30 minutes, after which was added(250 μL, 0.50 mmol) of 2 N HNCH₃ in MeOH and the stirring continued overnight. The reaction was concentrated and partitioned between a saturatedsolution of NaHCO₃ and ethyl acetate. The organic layer was separatedand the aqueous layer extracted 5 times with ethyl acetate. The organiclayers were dried (MgSO₄), filtered and concentrated to yield COMPOUND3. ¹H NMR (400 NM, CD₃OD): δ 1.07 (m, 3H), 1.21 (m, 3H), 2.32 (m, 2H),2.90 (s, 3H), 3.02 (m, 2H), 3.24 (m, 4H), 3.40 (m, 2H), 3.50 (m, 2H),4.34 (s, 2H), 4.55 (s, 1H), 7.33 (d, J=8.2 Hz, 2 H), 7.41 (m, 1H), 7.48(m, 5H), 7.56 (d, J=8.2 Hz, 2H), 7.63 (m, 2H), 7.93 (m, 1H)

COMPOUND 3 was separated by chiral HPLC to yield COMPOUNDS 3a and 3b,using a Chiralpak AD column with 35% isopropanol 65% Hexane as aneluent, retention time being 7.1 and 17.3 minutes for COMPOUNDS 3a and3b respectively.

For COMPOUND 3a, Purity (HPLC):>99%; Optical purity (Chiral HPLC):>99%.Found: C, 59.20; H, 5.94; N, 8.26. C₃₁H₃₈N₄O₂×1.6 C₂HO₂F₃×0.7 H₂O has C,59.21; H, 5.96; N, 8.08%

For COMPOUND 3b, Purity (BPLC):>97%; Optical purity (Chiral HPLC):>97%.Found: C, 59.73; H, 5.91; N, 8.32. C₃₁H₃₈N₄O₂×1.6C₂HO₂F₃×0.4 H2O: C,59.68; H, 5.92; N, 8.14%

1. A compound of formula I, pharmaceutically acceptable salts thereof,or mixtures thereof:

wherein R¹ is an aryl, heteroaryl, substituted aryl or substitutedheteroaryl; and R² is hydrogen, optionally substituted C₁₋₁₂alkyl,optionally substituted C₆₋₁₂aryl, or optionally substitutedC₂₋₁₂heterocyclyl.
 2. A compound according to claim 1, wherein R¹ isselected from phenyl; pyridyl; thienyl; furyl; imidazolyl; triazolyl;pyrrolyl; thiazolyl; and N-oxido-pyridyl, optionally substituted withone or more groups selected from C₁₋₆alkyl, halogenated C₁₋₆alkyl, —NO₂,—CF₃, C₁₋₆ alkoxy, chloro, fluoro, bromo, and iodo; and R² is hydrogenor methyl.
 3. A compound according to claim 1, wherein R¹ is selectedfrom phenyl; pyridyl; thienyl; furyl; imidazolyl; pyrrolyl; andthiazolyl, optionally substituted with one or more groups selected fromC₁₋₆alkyl, halogenated C₁₋₆alkyl, —NO₂, —CF₃, C₁₋₆ alkoxy, chloro,fluoro, bromo, and iodo; and R₂ is hydrogen or methyl.
 4. A compoundaccording to claim 1, wherein R¹ is selected from phenyl; pyridyl;thienyl; furyl; imidazolyl; pyrrolyl; and thiazolyl; and R² is hydrogenor methyl.
 5. A compound according to claim 1, wherein the compound isselected from:3-[(4-[(diethylamino)carbonyl]phenyl)(4-benzyl-piperazin-1-yl)methyl]benzamide;3-{(4-[(diethylamino)carbonyl]phenyl)[4-(2-furylmethyl)-piperazin-1-yl]methyl}benzamide;3-[[4-[(diethylamino)carbonyl]phenyl][4-(phenylmethyl)-1-piperazinyl]methyl]-N-methyl-benzamide;enantiomers thereof; and pharmaceutically acceptable salts thereof. 6-7.(canceled)
 8. A pharmaceutical composition comprising a compoundaccording to claim 1 and a pharmaceutically acceptable carrier.
 9. Amethod for the therapy of pain in a warm-blooded animal, comprising thestep of administering to said animal in need of such therapy atherapeutically effective amount of a compound according to claim
 1. 10.A method for the therapy of functional gastrointestinal disorders in awarm-blooded animal, comprising the step of administering to said animalin need of such therapy a therapeutically effective amount of a compoundaccording to claim
 1. 11. A process for preparing a compound of formulaII,

comprising of the step of reacting a compound of formula III:

with R¹—CHO to form the compound of formula II wherein R¹ is an aryl,heteroaryl, substituted aryl or substituted heteroaryl.
 12. A processfor preparing a compound of formula IV,

comprising: reacting a compound of formula II,

with an akali metal hydroxide in non-aqueous solvent to form thecompound of formula IV: wherein R¹ is an aryl, heteroaryl, substitutedaryl or substituted heteroaryl.